Transmission line voltage indicator



Mardi 4, 1947 D. A. HowARD, JR

TRANSMISSION LINE VOLTAGE INDICATOR Filed Jan. 2, 1945 l//Vf Flo INVENTOR. MM; A wwwa JA? v BY '/sfl #A HAMM/775s Patented Mar. 4, 1947 4UNITED STATES PATENT OFFICE TRANSMISSION LINE VOLTAGE INDICATOR I' David A. Howard, Jr., Hartwell, (la.

Application January 2, 1945, Serial No. 571,059

(Granted under the act of March 3, 1883, as

amended April 30, 1928; 370 O. G: 757) 4 Claims.

The invention described herein may be manuiactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

'I'he invention to be hereinafter described relates to indicators for tuning radio transmitters.

Heretofore, in such work, it has been common practice to use plate current milliammeters, thermocouple ammeters, light bulbs or Wattmeters employing dummy loads. Various disadvantages and objections are inherent in those instruments. Plate current miliammeters are often misleading and they are dii'licult for inexperienced personnel toV use. Thermocouple ammeters are slow acting. Light bulbsv must be actually built into the transmitter. They consume more current than required by the present invention. Wattmeters, employing dummy loads, representing an antenna load, seldom possess the same impedance as that of the antenna for which the dummy load has been substituted. They, too, are slow acting.

The main objects of the present invention are to completely overcome or minimize the above and other objections and provide a simple, compact, quick acting emcient instrument, usable over a Wide range of frequencies, readily transferable from one transmitter to another and capable of denitely revealing the presence and magnitude of standing waves.

In order to more clearly disclose the construction, operation and use of the invention, reference should be had to the accompanying drawings forming part of the present application.

Throughout the several gures of the drawings like reference characters designate the same parts in the different views. l

In the drawings:

Fig. 1 is a side elevation of the invention;

Fig. 2 is a cross section through Fig. 1, enlarged, showing in diagram, the electrical features; and

Figs. 3 and 4 are diagrammatic illustrations of the use of the invention.

Briefly referring to the drawings in detail, especially Fig. 2, the instrument of the invention comprises a suitable case, box, or housing T in which are disposed, according to the diagram shown, or its approximate equivalent, the following elements: A carbon resistor R of suitable vrangesuch as 25,000 ohms; a crystal rectifier X of very high frequency or microwave type; a condenser C cf, for instance, .001 m. f. d.; a. short section of coaxial line L; connection S for line L; and a meter jack J with plug in connection for suitable connection to a meter M, such as in any of the above mentioned types of meters."

Such deflection is a direct indication of the power output of the transmitter being tuned.

If the line is relatively free of standing waves the power output will be equal to E2 divided by R where R is the characteristic impedance of the transmission line, E being the voltage existing between the inner and outer conductors of the line. E may be read directly by Calibrating the equipment, although a relative reading is sum-- cient.

If standing waves are suspected on a transmission line the following procedure, with the use of this invention, will indicate their presence and magnitude. Two sections of line having the same characteristic impedance as the transmission line being investigated are connected in series with the transmitter and transmission line. Preferably, the sections should have 1A, wave and V8 wave electrical length. Figs. 3 and 4, collectively, indicate points (I 2,.3 and 4) at which the invention should be inserted, such connections being made in usual and well known manner.

The readings given at such conections will give the line voltage at the transmitter, 1/8 wave from the transmitter, 1A wave from the transmitter and wave' from the transmitter. By plotting these voltages against wave length, the standing wave ratio can be determined, thus revealing the existence and magnitude of the Suspected standing waves. Standard matching procedures may now be employed to eliminate the standing waves. When the standing waves have been eliminated the meter will indicate equal values at all four points (I, 2, 3 and 4).

Adaptation of the device for open wire lines will be well understood by those skilled in the art to which the invention relates.

It is thought that the construction, operation and use of the invention will be clear from the preceding detailed description.

Changes may be made in the construction and disposition of the various parts of the invention withinthe scope of the appended claims without departing from the neld of the invention, and it is meant to include all such within this application wherein only one preferred form has been illustrated purely by way oi' example and with no thought or intent of, in any degree, limiting the invention thereby.

Having thus described my invention, what I claim and desire toprotect by Letters Patent is:

1. An instrument for indicating the presence and magnitude of standing waves on a transmission line comprising a housing, a section of coaxial line mounted thereon and extending therethrough and provided with end connectors exterior to said housing whereby said instrument may be selectively inserted in a transmission line, a circuit in said housing and including said section of coaxial line, a resistor in said circuit, a crystal rectifier in series with said resistor in said circuit, a condenser in series with said Vresistor and said rectiiier in said circuit, and a jack in said circuit for plug-in connection.

2. An instrument for indicating the presence and magnitude oi standing waves on a transmission line comprising a'housing, a section of coaxial line mounted therein and extending therethrough animasY i and provided with end connectors exterior to and magnitude of standing waves on a transmission line comprising a housing, a section of coaxial line mounted therein and extending therethrough and provided with end connectors exterior to said housing whereby said instrument] may be selectively inserted in a transmission line, a circuit in said housing and including said section o'f coaxial line, a resistor in said circuit, a microwave type crystal rectifier in series with said resistor in said circuit, a condenser in series with said resistor and saidrectiiler in said circuit said rectiiier in said circuit, a condenser in series v- The following references are of record in the ille of this patent:

UNITED STATESA PATENTS Name Date Bowen Feb. 1, 1938 OTHER REFERENCES Practical Analysis of Ultra High Frequency" Number ,by Meagher and Markley, 2nd Edition, August,

1943, published by RCA Service Company, Inc., Camden, New Jersey, (copy in Division 42) 171- 95.23. 

